Pneumatic tires having riblike land portions in the shoulder regions (shoulder land portions) continuously along the circumference of the tire, such as heavy-duty pneumatic tires, are subject to heavy loads on the shoulder land portions when the vehicle accelerates, decelerates, or makes turns. A conventional problem with such pneumatic tires, therefore, has been the frequent occurrence of irregular wear in the shoulder land portions or cracking in the shoulder grooves.
In a proposed method for controlling irregular wear in the shoulder land portions, the inclination of the wall surface of the shoulder land portion facing a shoulder groove, for instance, is varied at predetermined intervals along the circumference of the tire (see Patent Document 1, for instance).
On the other hand, proposed methods for reducing the occurrence of cracking in shoulder grooves have relied on enlargement of the groove bottom radius of shoulder grooves, provision on the wall surface facing the shoulder groove of the shoulder land portion a first inclined part inclining toward the groove center from the perpendicular line from the tread face of the shoulder land portion and a second inclined part inclining further inclining toward the groove center from the first inclined part, and the like so as to raise the rigidity of the shoulder land portions (see Patent Documents 2 and 3, for instance).